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    <center>Scilab Function</center>
    <div align="right">Last update : April 1993</div>
    <p>
      <b>chart</b> -  Nichols chart</p>
    <h3>
      <font color="blue">Calling Sequence</font>
    </h3>
    <dl>
      <dd>
        <tt>chart([flags])  </tt>
      </dd>
      <dd>
        <tt>chart(gain [,flags])  </tt>
      </dd>
      <dd>
        <tt>chart(gain,phase [,flags])  </tt>
      </dd>
    </dl>
    <h3>
      <font color="blue">Parameters</font>
    </h3>
    <ul>
      <li>
        <tt>
          <b>gain</b>
        </tt>: real vector ( gains (in DB))</li>
      <li>
        <tt>
          <b>phase</b>
        </tt>: real vector (phases (in degree))</li>
      <li>
        <tt>
          <b>flags</b>
        </tt>: a list of at most 4 flags list(sup [,leg [,cm [,cphi]]])<ul>
          <li>
            <tt>
              <b>sup</b>
            </tt>: 1 indicates superposition on the previous plot   0 no superposition is done</li>
          <li>
            <tt>
              <b>leg</b>
            </tt>: 1 indicates that legends are drawn, o: no legends</li>
          <li>
            <tt>
              <b>cm</b>
            </tt>: color number (see plot2d) for gain curves</li>
          <li>
            <tt>
              <b>cphi</b>
            </tt>:  color number (see plot2d) for phase curves</li>
        </ul>
      </li>
    </ul>
    <h3>
      <font color="blue">Description</font>
    </h3>
    <p>
    plot the Nichols'chart.</p>
    <p>
    The default values for <tt>
        <b>gain</b>
      </tt> and <tt>
        <b>phase</b>
      </tt> are respectively :</p>
    <p>
      <tt>
        <b>[-12 -8 -6 -5 -4 -3 -2 -1.4 -1 -.5 0.25 0.5 0.7 1 1.4 2 2.3 3 4 5 6 8 12]</b>
      </tt>
    </p>
    <p>
      <tt>
        <b>[-(1:10) , -(20:10:160)]</b>
      </tt>
    </p>
    <h3>
      <font color="blue">Examples</font>
    </h3>
    <pre>

s=poly(0,'s')
h=syslin('c',(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01))
black(h,0.01,100,'(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01)')
chart(list(1,0,2,3));

xbasc()
h1=h*syslin('c',(s^2+2*0.1*15.1*s+228.01)/(s^2+2*0.9*15*s+225))
black([h1;h],0.01,100,['h1';'h'])
chart([-8 -6 -4],[80 120],list(1,0));
 
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